1. Field of the Invention
The present invention relates to a probe method, a prober, and an electrode reducing/plasma-etching process mechanism. More specifically, the present invention relates to a probe method, a prober, and an electrode reducing/plasma-etching process mechanism which can improve the electrical contact state of the electrode of an object to be tested and a probe pin.
2. Description of the Related Art
A process of manufacturing an electrical product and electrical component (e.g., a semiconductor) includes various steps such as a film formation step of forming various types of metal layers such as an interconnection layer on a target object (e.g., a wafer), a step of testing the object to be tested which is formed on the wafer, and a step of testing the packaged object to be tested. For example, to test the electrical characteristics of the object to be tested which is formed on the wafer, a probe pin is brought into contact with an electrode of the object to be tested. A measurement signal is applied to the object to be tested from a tester through the probe pin. If an electrically insulating oxide film has been formed on the surface of the electrode of the object to be tested, sometimes the electrode cannot be electrically connected to the probe pin by merely bringing the probe pin into contact with the electrode. In this case, a test signal cannot be applied to the electrode from the tester. Conventionally, while the probe pin is in contact with the electrode with a predetermined needle pressure, the probe pin scrubs the electrode surface to break the oxide film on the electrode surface, so that the probe pin and electrode are brought into electrical contact with each other.
As the integration degree of semiconductor products becomes ultra-high, the thicknesses of the deposition layers of the semiconductor products decrease acceleratingly. Electrodes also become thin. If the probe pin is brought into contact with the electrode with a needle pressure of a degree that barely breaks the oxide film, as in the conventional probe method, the needle pressure of the probe pin may undesirably change the electrical characteristics of the semiconductor product. When the lower layer of the electrode is made of a soft material such as a low-k material that has a low dielectric constant, the probe pin cannot be brought into contact with the electrode with such needle pressure.
In the film formation step, an oxide film on a metal layer hinders formation of another metal layer on it. Therefore, the oxide film must be reduced and removed in advance by cleaning or the like. For example, Jpn. Pat. Appln. KOKAI Publication No. 2000-311868 (claim 14 and paragraph [0041]) describes, in a process of forming a via hole for connecting different interconnection layers in a multilayered interconnection, a process of cleaning the via hole before forming an upper metal interconnection. In this process, a native oxide film and the like formed in the via hole in the surface of a silicon substrate are removed by using negative hydrogen ions generated by supplying electrons to hydrogen radicals. In this process, a gas containing hydrogen atoms is subjected to microwave discharge irradiation in a vacuum container, thus generating a hydrogen plasma. An electron supply device supplies thermoelectrons to the hydrogen radicals to generate negative hydrogen ions. In this reference, the negative hydrogen ions are used for cleaning.
In the testing step, a probe pin is brought into electrical contact with an electrode on the wafer surface. While the probe pin and electrode are in electrical contact with each other, testing of the object to be tested is performed. If an oxide film is present on the electrode surface, as the oxide film is an insulator, it interferes with electrical contact of the probe pin and electrode. For this reason, the oxide film on the electrode surface must be removed prior to testing. To remove the oxide film, a reducing method described in Jpn. Pat. Appln. KOKAI Publication No. 2000-311868 can be used. With this reducing method, however, the wafer is exposed to harsh conditions. Accordingly, elements formed on the wafer may be damaged, decreasing the yield.
U.S. Pat. No. 6,191,416 B1 (claims and the fourth column, 4 to 16 lines) describes an apparatus which generates free atoms or radical particles. This apparatus has a tube for supplying a gas, e.g., hydrogen gas or halogen gas, and a wire extending along the tube and connected to a power supply. A current is supplied to the wire to heat it. The radiation heat of the wire heats the gas flowing in the tube to 1,500° K to 2,500° K, to thermally decompose the gas, thus forming an atomic material or radicals. The atomic material or radicals of the gas serve to reduce other materials. This apparatus is compact and inexpensive when compared to that of Jpn. Pat. Appln. KOKAI Publication No. 2000-311868. However, the tube must be heated to a high temperature.
“Characterization of Cu surface cleaning by hydrogen plasma”, M. R. Baklanov, D. G. Shamiryan, Zs. Tokei, G. P. Beyer, T. Conard, S. Vanhaelemeersch, and K. Maexj. Vac. Sci. Technol. B19(4), July/August 2001 (preface of page 1,201) reports a technique of thermally decomposing such copper oxide, copper hydroxide, and the like into water or the like and copper oxide in a vacuum at a temperature of 150° C. or more to remove water or the like from the metal surface, and reducing and removing the remaining copper oxide with a hydrogen plasma.
According to the technique described in U.S. Pat. No. 6,191,416 B1, hydrogen radicals and atomic hydrogen can be generated from the hydrogen gas with a comparatively simple apparatus. However, the reducing ability of the hydrogen radicals and atomic hydrogen is not clear.
According to “Characterization of Cu surface cleaning by hydrogen plasma”, copper oxide, hydroxide, and the like on the copper metal surface are reduced in a vacuum by using the hydrogen plasma at the temperature of 150° C. or more. Therefore, reduction must be performed in a vacuum atmosphere in the same manner as in Jpn. Pat. Appln. KOKAI Publication No. 2000-311868.